Back to EveryPatent.com
| United States Patent |
5,096,958
|
|
Meguro
, et al.
|
March 17, 1992
|
Hydrophilic surface treatment chemicals, hydrophilic surface treatment
bath, and hydrophilic surface treatment method
Abstract
A hydrophilic surface treatment chemicals comprising, on a solid basis,
(a) 1-10 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 0.3-15 parts by weight of water-soluble nylon, and
(c) 0.1-5 parts by weight of a water-soluble amino resin,
a weight ratio of the component (b) to the total of the components (a) and
(c), (b)/[(a)+(c)], being in the range of 1-1/4, and a weight ratio of the
component (a) to the component (c), (a)/(c), being in the range of
1/0.05-1/0.5. The hydrophilic surface treatment bath is prepared by
properly diluting the chemicals for surface-treating aluminum members.
| Inventors:
|
Meguro; Shigeyuki (Yokohama, JP);
Yasuhara; Kiyotada (Yokohama, JP)
|
| Assignee:
|
Nippon Paint Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
565087 |
| Filed:
|
August 10, 1990 |
Foreign Application Priority Data
| Current U.S. Class: |
524/503; 427/327; 427/435; 524/514; 525/58 |
| Intern'l Class: |
C08L 029/04 |
| Field of Search: |
252/392
106/14.15,14.41,14.42
524/503,514
525/58
427/327,435
|
References Cited
U.S. Patent Documents
| 3386940 | Jun., 1968 | Tuites | 524/503.
|
| 4828616 | May., 1989 | Yamasoe | 106/14.
|
| Foreign Patent Documents |
| 55-12375 | Jan., 1980 | JP.
| |
| 56-56572 | May., 1981 | JP.
| |
Other References
English abstract of JP-A 60-50397.
English abstract of JP-A 61-250495.
English abstract of JP-A 62-132970.
English abstract of JP-A 62-176578.
|
Primary Examiner: Lusignan; Michael
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Claims
What is claimed is:
1. A hydrophilic surface treatment chemical comprising on a solid basis,
(a) 2-5 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 1-5 parts by weight of water-soluble nylon having at least one group
selected from a hydroxy group and an amino group, and
(c) 0.5-2 parts by weight of a water-soluble amino resin, a weight ratio of
component (b) to a total of components (a) and (c), (b)/((a)+(c)) being in
the range of 1-1/4, and a weight ratio of component (a) to component (c),
(a)/(c) being in the range of 1/0.05-1/0.5.
2. The hydrophilic surface treatment chemical according to claim 1, wherein
said water-soluble amino resin is a water-soluble melamine resin.
3. An aqueous hydrophilic surface treatment bath comprising, on a solid
basis,
(a) 2-5 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 1-5 parts by weight of water-soluble nylon having at least one group
selected from a hydroxy group and an amino group, and
(c) 0.5-2 parts by weight of a water-soluble amino resin, a weight ratio of
component (b) to a total of components (a) and (c), (b)/((a)+(c)) being in
the range of 1-1/4, and a weight ratio of component (a) to component (c),
(a)/(c) being in the range of 1/0.05-1/0.5.
4. The aqueous hydrophilic surface treatment bath according to claim 3,
wherein said water-soluble amino resin is a water-soluble melamine resin.
Description
BACKGROUND OF THE INVENTION
The present invention relates to aqueous surface treatment chemicals for
forming hydrophilic coatings on aluminum members such as heat exchanger
fins, etc., a bath containing such surface treatment chemicals, and a
method of surface-treating an aluminum member with such an aqueous surface
treatment bath. More particularly, it relates to hydrophilic surface
treatment chemicals for forming hydrophilic coatings with good corrosion
resistance and high hydrophilic nature and also with no or extremely
reduced odor on aluminum members such as fins of heat exchangers, a bath
containing such a surface treatment chemicals and a method of treating
them.
Aluminum and its alloys are light and have good workability and heat
conductance, so that they are widely used for fins of heat exchangers.
Recently more and more air conditioners have been used not only for
cooling but also for warming and dehumidification. In heat exchanger parts
of these air conditioners, aluminum alloy fins are generally used.
However, it is observed that moisture tends to be condensed and deposited
as water droplets on the fin surfaces of air conditioners during cooling
operations. If the fin surface is water-repellent, this condensed water
tends to be deposited in a hemispherical form on the fin surface or forms
bridges between the fins, preventing smooth air flow, which in turn
increases resistance of air flow, thereby decreasing heat exchange
efficiency.
In addition, although aluminum and its alloys are essentially excellent in
corrosion resistance, it is likely that the condensed water remaining on
the aluminum fin surfaces for a long period of time functions like an
oxygen concentration cell, and that contaminants and sulfur oxides in the
air are absorbed and concentrated in the condensed water. As a result, a
hydration reaction and a corrosion reaction are accelerated. Those
produced by the corrosion are accumulated on the aluminum fin surfaces,
which not only deteriorate heat exchange performance, but also are blown
out of the air conditioners as white fine powders together with hot air
during the warming operation in the winter season.
To solve these problems, various attempts have been made to form on
aluminum fin surfaces coatings for improving their corrosion resistance
and for increasing their hydrophilic nature.
For instance, Japanese Patent Laid-Open Nos. 55-12375 and 56-56572 disclose
evaporators having fins coated with synthetic resins comprising
hydrophilic amides. A water-soluble nylon is chosen as a resin for coating
the fins of these evaporators.
Japanese Patent Laid-Open No. 61-250495 discloses an aluminum fin having a
chemical primer coating and a coating which comprises organic polymer
materials such as water-soluble polyamides showing cationic
characteristics in an aqueous solution.
Further, Japanese Patent Laid-Open No. 63-57674 discloses hydrophilic
surface treatment chemicals comprising a water-soluble resin such as
water-soluble nylon, an alkali metal silicate and an amino alcohol.
Furthermore, Japanese Patent Laid-Open No. 62-132970 discloses surface
treatment chemicals for treating fins of a heat exchanger, which comprises
(A) an adduct of (a) at least one of urea, thiourea and guanidine and (b)
formalin, or a condensate of the adduct, and (B) a water-soluble nylon.
Japanese Patent Laid-Open No. 62-176578 discloses a method of surface
treatment by using the above chemicals.
However, any one of the coatings disclosed in the above references fails to
have good hydrophilic nature and sufficient effect of preventing odor.
An aluminum-made heat exchanger provided with a coating comprising a
water-insoluble germicide to kill microorganisms in water droplets
condensed on the fins, etc., thereby preventing unacceptable odor caused
by the microorganisms is disclosed in Japanese Patent Laid-Open No.
60-50397, but this coating is still insufficient in hydrophilic nature and
odor-preventing effect.
As mentioned above, the conventional surface treatment technologies for
heat exchangers fail to provide coatings which have not only sufficient
hydrophilic nature. corrosion resistance and strength but also excellent
odor-preventing effect.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide hydrophilic
surface treatment chemicals for forming hydrophilic coatings having
excellent hydrophilic nature, corrosion resistance and water dissolution
resistance with substantially no odor, on heat exchanger fins, etc.
Another object of the present invention is to provide a surface treatment
bath containing such surface treatment chemicals.
A further object of the present invention is to provide a method for
forming a hydrophilic coating with such properties on an aluminum member.
As a result of intense research in view of the above object, the inventors
have found that a combination of at least partially saponified polyvinyl
acetate, a water-soluble nylon and a water-soluble amino resin in
particular proportions can provide a coating having good hydrophilic
nature and corrosion resistance with substantially no odor. The present
invention is based on this finding.
Thus, the surface treatment chemicals according to the present invention
comprise, on a solid basis,
(a) 1-10 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 0.3-15 parts by weight of water-soluble nylon, and
(c) 0.1-5 parts by weight of a water-soluble amino resin,
a weight ratio of the component (b) to the total of the components (a) and
(c), (b)/[(a)+(c)], being in the range of 1-1/4, and a weight ratio of the
component (a) to the component (c), (a)/(c). being in the range of
1/0.05-1/0.5.
The surface treatment bath according to the present invention comprises, on
a solid basis.
(a) 1-10 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 0.3-15 parts by weight of water-soluble nylon, and
(c) 0.1-5 parts by weight of a water-soluble amino resin,
a weight ratio of the component (b) to the total of the components (a) and
(c), (b)/[(a)+(c)], being in the range of 1-1/4, and a weight ratio of the
component (a) to the component (c), (a)/(c), being in the range of
1/0.05-1/0.5.
The method of surface-treating aluminum or its alloy according to the
present invention comprises the steps of degreasing said aluminum or alloy
thereof and treating it with a hydrophilic surface treatment bath which
comprises, on a solid basis.
(a) 1-10 parts by weight of at least partially saponified polyvinyl acetate
having a saponification degree of 45 or more and a polymerization degree
of 100-600,
(b) 0.3-15 parts by weight of water-soluble nylon, and
(c) 0.1-5 parts by weight of a water-soluble amino resin,
a weight ratio of the component (b) to the total of the components (a) and
(c), (b)/[(a)+(c)], being in the range of 1-1/4, and a weight ratio of the
component (a) to the component (c), (a)/(c), being in the range of
1/0.05-1/0.5.
DETAILED DESCRIPTION OF THE INVENTION
Hydrophilic Surface Treatment Chemicals
(a) At least partially saponified polyvinyl acetate
At least partially saponified polyvinyl acetate used in the present
invention is expressed by the general formula:
##STR1##
wherein m represents the number of saponified structure units, and n
represents the number of unsaponified structure units.
This high-molecular compound is also called polyvinyl alcohol.
The above at least partially saponified polyvinyl acetate should have a
degree of saponification of 45 or more, and a degree of polymerization
(m+n) of 100-600. The degree of saponification and the degree of
polymerization herein are based on JIS K6725 5.2 and JIS K6725 5.4,
respectively.
When the degree of polymerization is less than 45 or the degree of
polymerization exceeds 600, sufficient hydrophilic nature cannot be
obtained. On the other hand, when the degree of saponification is less
than 100, a film-forming property and odor-suppressing effects are
lowered. The preferred degree of saponification is 80 or more, and the
preferred degree of polymerization is 200-550.
The at least partially saponified polyvinyl acetate having a degree of
saponification of 45 or more and a degree of polymerization of 100-600
functions to suppress odor and to improve hydrophilic nature. To achieve
these functions effectively, the at least partially saponified polyvinyl
acetate is used in an amount of 1-10 parts by weight on a solid basis in
the surface treatment chemicals. When it is less than 1 part by weight, it
fails to give high hydrophilic nature expressed by a contact angle of
water. On the other hand, when it exceeds 10 parts by weight, the problems
of unacceptable odor and a poor film-forming ability arise. The preferred
amount of the at least partially saponified polyvinyl acetate is 2-5 parts
by weight.
Incidentally, in addition to the above range, the amount of the at least
partially saponified polyvinyl acetate in the surface treatment chemicals
should meet the conditions of a particular weight ratio to other
components (water-soluble nylon and a water-soluble amino resin) to
achieve excellent hydrophilic nature and odor-suppressing effect. The
details will be described later.
(b) Water-soluble nylon
The water-soluble nylons used in the present invention are the ones
modified to be soluble in water and/or alcohol. Nylons to be modified for
use in the present invention may be nylon 6, nylon 66, etc. Among them,
nylon 6 is preferable. The average degree of polymerization of the
water-soluble nylon is in the range of 50-300, preferably 80-200. Such
water-soluble nylons are commercially available, including, for example,
AQ-nylon A-90, A-70, A-50, P-70, P-50, etc. (products of Toray Industries.
Inc.) .
The water-soluble nylon has a function to give good hydrophilic nature to
the coating. To achieve this function effectively, the amount of the
water-soluble nylon is 0.3-15 parts by weight on a solid basis in the
hydrophilic surface treatment chemicals. When the amount of the
water-soluble nylon is less than 0.3 parts by weight, the film-forming
property becomes poor and the odor-suppressing effects turn insufficient.
On the other hand, when it exceeds 15 parts by weight the hydrophilic
nature of the resulting coating decreases. The preferred amount of the
water-soluble nylon is 1-5 parts by weight.
The water-soluble nylon itself is water soluble and its hydrophilic groups
remain intact even after the baking and drying of the coating, so that it
does not lose its hydrophilic nature. Such water soluble nylon has at
least one of a hydroxy group and an amino group, and secondary amines,
tertiary amines, and alkanol amines may be bonded to nylon to impart
water-solubility to the nylon. As secondary amines, aliphatic amines such
as ethylenediamine, trimethylenediamine, tetramethylenediamine,
pentamethylenediamine (cadaverine) hexamethylenediamine,
1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane,
1,10-diaminodecane, etc., and aromatic amines such as o-phenylenediamine,
m-phenylenediamine p-phenylenediamine, etc., may be used. As the tertiary
amines, triethyl amine, tripropyl amine, tributyl amine, dimethylbenzyl
amine, etc., may be used. As for alkanol amines, ethanol amine, diethanol
amine, triethanol amine, amino ethyl ethanol amine, morpholine, etc., may
be used.
(c) Water-soluble amino resin
The water-soluble amino resins used in the present invention include
melamine resins such as n-butylated melamine resin, iso-butylated melamine
resin, benzoguanamine resins, urea resins, etc., which are modified to
have water solubility. These resins may usually be prepared by carrying
out an addition reaction or an addition condensation reaction of amino
resins with aldehydes such as formaldehyde, para-formaldehyde, etc., and
then subjecting the resulting compound to etherification with
water-soluble monovalent alcohols having 1-4 carbon atoms. Among the
water-soluble amino resins mentioned above, the water-soluble melamines
are preferable.
The melamine resins used for the preparation of the water-soluble melamines
are alkoxymethyl melamines having alkoxy groups such as methoxy, ethoxy,
n-butoxy, i-butoxy, etc., and methylated melamine is preferable.
The water-soluble amino resin acts as a cross-linking agent to improve the
film-forming property of the chemicals. To achieve this function
effectively, the amount of the water-soluble amino resin is 0.1-5 parts by
weight on a solid basis in the surface treatment chemicals. When the
amount of the water-soluble amino resin is less than 0.1 parts by weight,
film-forming property of the surface treatment chemicals becomes poor, and
the odor problem arises. When the amount of the water-soluble amino resin
is more than 5 parts by weight, the hydrophilic nature of the coating is
poor. The preferred amount of the water-soluble amino resin is 0.5-2 parts
by weight.
The water-soluble amino resin itself is water soluble, and its hydrophilic
groups remain intact after baking and drying of the coating, so that it
does not lose its hydrophilic nature, like the water-soluble nylon. Such a
water-soluble amino resin has at least one of secondary amines, tertiary
amines and alkanol amines, which are listed in (b) above. The
water-soluble amino resin may also have hydroxyl groups.
(d) Ratio of (a)-(c)
The surface treatment chemicals of the present invention comprise three
components (a), (b) and (c). To provide a hydrophilic coating having
excellent hydrophilic nature without odor, the amount of each component in
the surface treatment chemicals is required to meet, in addition to the
above-mentioned conditions, the following conditions:
(i) A weight ratio of (b) water-soluble nylon to the total amount of (a) at
least partially saponified polyvinyl acetate and (c) water-soluble amino
resin, (b)/[(a)+(c)], is in the range of 1-1/4 on a solid basis; and
(ii) A weight ratio of (a) at least partially saponified polyvinyl acetate
to (c) water-soluble amino resin, (a)/(c) , is in the range of
1/0.05-1/0.5 on a solid basis.
When the ratio of (b)/((a)+(c)) is less than 1/4, the hydrophilic nature is
insufficient. On the other hand, when it exceeds 1, the odor-suppressing
effects and the film-forming ability become poor. The preferred weight
ratio of (b)/[(a)+(c)] is 1/3-1/1.5.
When the weight ratio of (a)/(c) is less than 1/0.5, the film-forming
property and the odor-suppressing effects are insufficient even though the
hydrophilic nature is sufficient. When it exceeds 1/0.05, the hydrophilic
nature becomes insufficient. The preferred weight ratio of (a)/(c) is
1/0.4-1/0.1.
(e) Other additives
The surface treatment chemicals for forming a hydrophilic coating according
to the present invention may contain, in addition to the above
indispensable components, surfactants, mildew-proofing agents, antiseptics
(bactericides), water glass and/or colloidal silica in such amounts as not
to generate odor, small amounts of solvents, etc.
The surfactants may be nonionic, cationic, anionic or ampholytic ones, and
any suitable surfactants may be selected by taking into consideration the
stability, foamability, coatability, etc., of the surface treatment
chemical solution.
Typical examples of nonionic surfactants which may be used include
polyoxyethylene glycol, polyoxypropylene glycol,
polyoxyethylene-polyoxypropylene glycol, polyoxyethylene alkylphenyl
ether, glycerin-aliphatic acid esters, sorbitan-aliphatic acid esters,
pentaerythritol aliphatic acid esters, polyoxyethylene sorbitan aliphatic
acid esters, polyethylene alkyl ethers, etc.
Typical examples of anionic surfactants which may be used include
dialkylsulfosuccinates, alkane sulfonates, alkylbenzene sulfonates,
alkylnaphthalene sulfonates, polyoxyethylene alkyl sulfophenyl ether
salts, alkyl phosphates, polyoxyethylene alkyl ether-phosphates, aliphatic
alkyl ester-sulfates, alkyl sulfates, polyoxyethylene alkyl
ether-sulfates, aliphatic acid monoglyceride-sulfates, etc.
Typical examples of cationic surfactants which may be used include alkyl
amine salts, dialkyl amine salts, etc.
Typical examples of ampholytic surfactants may be N,N,N-trialkyl-N-sulfo
alkylene ammonium betaine, etc.
The amount of the surfactants added is preferably 0.5 parts by weight or
less. When it exceeds 0.5 parts by weight, the water resistance of the
resulting coating decreases.
As for the mildew-proofing agents and the antiseptics (bactericides),
quaternary ammonium salts, nitrogen-containing sulfur compounds,
halogen-containing nitrosulfur compounds, organic iodine compounds,
benzimidazole and its derivatives, etc., may be used.
Typical examples of the mildew-proofing agents include 2-thiazol-4-yl
benzimidazole, methylbenzimidazol-2-yl carbamate, N-dichlorofluoromethyl
thio-N',N'-dimethyl-N-phenylsulfamide, tetramethyl thiuram disulfide,
N-(trichloromethyl thio) -4-cyclohexene-1, 2-dicarboxyimide,
2,4,5,6-tetrachloro-1 3,-isophthalonitrile
2,3,5,6-tetrachloro-4-(methylsulfonyl) pyridine etc. Considering the heat
resistance of the resulting hydrophilic coating, 2-thiazol-4-yl
benzimidazole, methylbenzimidazol-2-yl carbamate, and
2,4,5,6-tetrachloro-1,3,-isophthalonitrile are preferable.
Typical examples of the bactericides include 1,2-benzo isothiazoline-3-on
(BIT) , 2.3,5,6-tetrachloro-4-(methylsulfonyl) pyridine,
10,10'-oxybisphenoxarsine, etc.
The preferable amounts of the mildew-proofing agents and the bactericides
are 0.1-1.5 parts by weight in total.
The addition of water glass and/or colloidal silica to the surface
treatment chemicals in such amounts as not to generate odor may improve
the hydrophilic nature. As the water glass, SiO.sub.2 /M.sub.2 O (where M
represents Li, Na and K) may be used, and SiO.sub.2 /K.sub.2 O is
particularly preferable. Colloidal silica having an average particle
diameter of 10-50 .mu.m is preferable. Their total amount is preferably
less than 1 part by weight.
Further, solvents may be added to the surface treatment chemicals for the
improvement of the wettability of the resulting hydrophilic coating. Such
solvents include alcohols and cellosolves. Their amounts are preferably
less than 7 parts by weight.
Surface treatment bath
The surface treatment bath for forming a hydrophilic coating on an aluminum
member according to the present invention is produced by properly diluting
the above surface treatment chemicals. The percentages of the components
in the bath are as described above. The concentration of the surface
treatment bath is usually adjusted so as to provide a hydrophilic coating
of 0.5-1.5 g/m.sup.2 to an aluminum plate by dipping, spraying, brushing,
etc. In general, the concentration of solid components in the bath may be
10-200 g/l. If some of the components decrease unproportionally, they
should be supplemented in order to maintain the percentage of each
component at a proper level.
Surface treatment method
Before forming a coating layer with the surface treatment bath, a
degreasing treatment is usually conducted. The degreasing treatment
includes an acid-washing treatment using sulfuric acid, nitric acid, etc:
solvent degreasing using trichloroethylene, perchloroethylene, gasoline,
n-hexane, etc., and alkali degreasing using alkali solutions of sodium
hydroxide, sodium carbonate, sodium silicate, sodium phosphate, etc.
After degreasing, a chemical treatment is conducted to form a
corrosion-resistant layer on a degreased aluminum member. The
corrosion-resistant layer can be obtained by a chromate treatment. The
chromate treatment is conducted with a treatment liquid containing chromic
acid and sulfuric acid, nitric acid, fluoric acid, phosphoric acid, etc.
and proper additives.
The chromate treatment is categorized into two groups; a phosphoric
chromate treatment using phosphoric acid as an inorganic acid, and a
chromium chromate treatment using the other acids. From the viewpoint of
corrosion resistance, the latter is better. The chromate treatment can be
conducted by immersion in a treatment liquid, or spraying the treatment
liquid. However, to fit exchanger's fins having complicated shapes, an
immersion method is easier. The corrosion-resistant layer obtained by the
chromate treatment has a Cr content of 50-150 mg/m.sup.2. When it is less
than 50 mg/m.sup.2, the layer does not have sufficient corrosion
resistance. On the other hand, when it exceeds 150 mg/m.sup.2, its
reaction with the hydrophilic layer takes place, resulting in the
deterioration of its hydrophilic nature. The aluminum member formed with
the corrosion-resistant layer is then washed with water. This is
preferably done with flowing water for 10-30 seconds or so.
In addition to the above chromate treatment, a chemical treatment can also
be conducted by using a zirconium treating agent. The zirconium treating
agent may be a mixture of polyacrylic acid and zirconium fluoride, etc. A
layer produced by this zirconium treatment agent has a Zr content of
0.1-40 mg/m.sup.2. Like the Cr content, when the Zr content is less than
0.1 mg/m.sup.2, sufficient corrosion resistance cannot be obtained, and
when it exceeds 40 mg/m.sup.2, the hydrophilic nature rather decreases.
When the zirconium treatment is conducted after the chromate treatment,
larger effects can be obtained.
The surface treatment chemicals of the present invention is diluted
properly as a bath, and applied to the aluminum surface subjected to
degreasing and the above chemical treatment. This can be done by a
roll-coating method, a bar-coating method, an immersion method, a spraying
method, a brushing method, etc. In a case where a treated member has a
complicated shape like heat exchanger fins, the immersion method is
preferable.
Incidentally, the surface treatment bath of the present invention may be
applied not only to shaped aluminum members such as fins but also to
aluminum plates which are to be shaped after coating.
EXAMPLES 1-7
Aluminum plates are degreased and then subjected to a phosphoric chromate
treatment by an immersion method with Alsurf 407/47 (tradename,
manufactured by Nippon Paint Co., Ltd.) to form a corrosion-resistant
coating having 80-120 mg/m.sup.2 of Cr content. These chromate-treated
aluminum plates are washed with tap water for 20 seconds.
Each of the aluminum plates is then dipped in a surface treatment solution
having the composition shown in Table 1 for 1 minute at a room
temperature, and then dried at 180.degree. C. for 20 minutes to form a
hydrophilic coating. Each of the resulting hydrophilic coatings is tested
with respect to odor, hydrophilic nature, water dissolution resistance,
adhesion and mildew-proofing. The test procedures and the evaluation
standards of test results are as follows:
(1) Odor test
Each aluminum plate formed with a hydrophilic coating (hereinafter referred
to simply as "sample") is subjected to an odor test and evaluated as
follows:
Excel.: No odor
Good: Only slight odor
Fair: Medium odor
Poor: Strong odor
(2) Test of hydrophilic nature (Test of contact angle of water)
Each sample is tested with respect to initial hydrophilic nature and
hydrophilic nature after wetting cycle, by measuring the contact angle of
water droplet.
(a) Hydrophilic nature at the initial stage (Initial hydrophilic nature)
5 .mu.l of deionized water is dropped onto a flat surface of each sample
held horizontally to measure a contact angle Q of a water droplet by a
goniometer. The contact angle Q is classified into the following
categories:
Excel.: Q<20.degree.
Good: 20.degree..ltoreq.Q<30.degree.
Fair: 30.degree..ltoreq.Q<40.degree.
Poor: 40.degree..ltoreq.Q
(b) Hydrophilic nature after wetting cycle
Each sample is subjected to five cycles of wetting treatments, each of
which consists of keeping it in contact with tap water at 50.degree. C.
for one minute and drying it at 120.degree. C. for 10 minutes. After that,
a contact angle Q of a water droplet is measured and classified in the
same manner as in the above test (a) .
(3) Water dissolution resistance
Each sample is dipped in tap water for 24 hours, and the weight of the
coating is measured before and after dipping to determine a water
dissolution ratio by the following equation:
Water dissolution=[(initial coating weight-ratio (%) coating weight after
24-hour dipping).div.initial coating weight].times.100
The evaluation standards of water dissolution resistance are as follows:
Excel.: less than 10%;
Good: 10% or more and less than 30%;
Fair: 30% or more and less than 50%; and
Poor: 50% or more.
(4) Adhesion Test
Cross-cut test is performed on each sample by the following procedure:
Straight cut lines perpendicular to each other are formed on each sample
with an interval of 1 mm to have 100 square cut pieces. An adhesive tape
is sticked to the cross-cut surface of each sample and then peeled off.
The number of the square pieces of the coating which remain on the
aluminum member is counted and classified as follows:
Excel 100;
Good: 90-99;
Fair: 80-89;
Poor: 70-79; and
Very poor: less than 70.
(5) Mildew-proofing test
According to JIS Z 2911, each sample of 3 cm.times.3 cm is immersed in
flowing water for 250 hours, and then a suspension containing four kinds
of spores shown below is sprayed to the sample. The resulting sample is
kept for incubation at 27.degree. C. for 7 days. After the incubation, the
propagation of the fungi on the sample is observed and classified into the
following categories:
Funqus:
Aspergillus niger IFO 4414
Penicillium funiclosum IFO 6345
Cladosporium cladosporioides IFO 6348
Aureobasidium pullulans IFO 6353
Categories:
Excel.: No propagation of the fungi observed by the naked eye.
Good Slight propagation of the fungi observed by the naked eye.
Fair: The fungi observed by the naked eye covers 1/3 of the surface of the
sample.
Poor: The fungi observed by the naked eye covers 2/3 of the surface of the
sample.
Very poor: The fungi observed by the naked eye covers substantially the
entire surface of the sample.
The results of the tests (1)-(5) are shown in Table 2.
TABLE 1
__________________________________________________________________________
Example No.
1 2 3 4 5 6 7 8 9 10 11 12
__________________________________________________________________________
Polyvinyl Acetate.sup.(1)
Saponification Degree
90 90 90 90 90 90 90 90 90 60 90 90
Polymerization Degree
500 500 500 500 500 500 500 500 500 200 500 500
weight % 3.5 3.5 3.5 9.5 1.0 5.0 1.0 3.5 10.0
3.5 3.5 3.5
Water-Soluble Nylon.sup.(2)
1.7 1.7 2.6 14.0
0.6 2.2 0.4 1.7 6.0 1.7 1.7 1.7
(weight %)
Water-Soluble Amino Resin
Type.sup.(3) M M M M M M M M M M U M
weight % 0.8 0.8 0.8 4.5 0.5 0.5 0.1 1.3 5.0 0.8 0.8 0.8
Mildew-Proofing Agent.sup.(4)
0.3 0.5 0.3 0.3 0.3 0.3 0.3 0.3 0.05
0.3 0.3 0.3
(weight %)
Bactericide.sup.(5) (weight %)
0.1 0.5 0.1 0.1 0.1 0.1 0.1 0.1 0.05
0.1 0.1 0.1
Additives
Type -- -- -- -- -- -- -- -- -- -- -- Butanol
weight % -- -- -- -- -- -- -- -- -- -- -- 5
Weight Ratio
(b)/((a) + (c)).sup.(6)
1/2.53
1/2.53
1/1.65
1/1.00
1/2.50
1/2.50
1/2.75
1/2.82
1/2.50
1/2.53
1/2.53
1/2.53
(a)/(c).sup.(7)
1/0.23
1/0.23
1/0.23
1/0.47
1/0.50
1/0.10
1/0.10
1/0.37
1/0.50
1/0.23
1/0.23
1/0.23
__________________________________________________________________________
Example No.
13 14 15 16 17
__________________________________________________________________________
Polyvinyl Acetate.sup.(1)
Saponification Degree
90 90 90 90 90
Polymerization Degree
500 500 500 500 500
weight % 3.5 3.5 3.5 3.5 3.5
Water-Soluble Nylon.sup.(2)
1.7 1.7 1.7 1.7 1.7
(weight %)
Water-Soluble Amino Resin
Type.sup.(3) M M M M M
weight % 0.8 0.8 0.8 0.8 0.8
Mildew-Proofing Agent.sup.(4)
0.3 0.3 0.3 0.3 0.3
(weight %)
Bactericide.sup.(5) (weight %)
0.1 0.1 0.1 -- 0.1
Additives
Type Isopropyl Alcohol
Water Glass
Colloidal Silica.sup.(8)
-- Surfactant.sup.(9)
8
weight % 5 0.3 0.3 -- 0.1
Weight Ratio
(b)/((a) + (c)).sup.(6)
1/2.53 1/2.53 1/2.53 1/2.53
1/2.53
(a)/(c).sup.(7)
1/0.23 1/0.23 1/0.23 1/0.23
1/0.23
__________________________________________________________________________
Note
.sup.(1) At least partially saponified polyvinyl acetate selected from:
(a) SMR30HH manufactured by ShinEtsu Chemical Co., Ltd., having a
saponification degree of 90 and a polymerization degree of 500; and
(b) SMR10M manufactured by ShinEtsu Chemical Co., Ltd. having a
saponification degree of 60 and a polymerization degree of 200.
.sup.(2) AQ Nylon P70 having average degree of polymerization of about 10
(manufactured by Toray Industries, Inc.)
.sup.(3) M: Watersoluble methylmelamine (NIKALAC MX054 manufactured by
Sanwa Chemical Co., Ltd.)
U: Watersoluble urea resin (EIBOND UL3201S manufactured by GunEi Chemical
Industries, Ltd.)
.sup.(4) COATCIDE 55D manufactured by Takeda Chemical Industries, Ltd.
.sup.(5) SLAOFF 72N manufactured by Takeda Chemical Industries, Ltd.
.sup.(6) Weight ratio of watersoluble nylon to (at least partially
saponified polyvinyl acetate + watersoluble amino resin).
.sup.(7) Weight ratio of at least partially saponified polyvinyl acetate
to watersoluble amino resin.
.sup.(8) SNOWTEX N manufactured by Nissan Chemical Industries, Ltd.
.sup.(9) PELEX SSH manufactured by Kao Corporation.
TABLE 2
______________________________________
Hydrophilic
Nature Water
Ex- After Dissolu- Mildew-
ample At Wetting
tion Re-
Ad- Proofing
No. Odor Start Cycle sistance
hesion
Property
______________________________________
1 Excel. Excel. Good Excel. Excel.
Excel.
2 Excel. Excel. Good Excel. Excel.
Excel.
3 Excel. Excel. Good Excel. Excel.
Excel.
4 Good Excel. Excel. Good Good Good
5 Excel. Good Good Excel. Excel.
Excel.
6 Excel. Excel. Good Excel. Excel.
Excel.
7 Excel. Excel. Good Excel. Excel.
Excel.
8 Excel. Good Good Excel. Excel.
Excel.
9 Excel. Good Good Excel. Excel.
Good
10 Excel. Good Good Excel. Excel.
Excel.
11 Excel. Excel. Good Excel. Excel.
Excel.
12 Excel. Excel. Good Excel. Excel.
Excel.
13 Excel. Excel. Good Excel. Excel.
Excel.
14 Excel. Excel. Excel. Excel. Excel.
Excel.
15 Excel. Excel. Good Excel. Excel.
Excel.
16 Excel. Excel. Good Excel. Excel.
Good
17 Excel. Excel. Excel. Excel. Excel.
Excel.
______________________________________
COMPARATIVE EXAMPLES 1-15
Aluminum plates are subjected to a chemical treatment in the same way as in
Example 1, and hydrophilic coatings are formed under the same conditions
as in Example 1 except for using surface treatment baths shown in Table 3.
The same tests as in Example 1 are carried out on the resulting plates. The
results are shown in Table 4.
TABLE 3
__________________________________________________________________________
Comparative Example No.
1 2 3 4 5 6 7 8
__________________________________________________________________________
Polyvinyl Acetate.sup.(1)
Saponification Degree
90 90 90 90 90 90 -- 90
Polymerization Degree
500 500 500 500 500 500 -- 500
weight % 3.5 3.5 3.5 3.5 0.5 12.0
-- 3.5
Water-Soluble Nylon.sup.(2)
1.7 1.7 0.1 20 1.7 1.7 1.7 --
(weight %)
Water-Soluble Amino Resin
Type.sup.(3) M M M M M M M M
weight % 0.05
7 0.8 0.8 0.8 0.8 0.8 0.8
Mildew-Proofing Agent.sup.(4)
0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3
(weight %)
Bactericide.sup.(5) (weight %)
0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Weight Ratio
(b)/((a) + (c)).sup.(6)
1/2.09
1/6.18
1/43
1/0.22
1/0.76
1/7.53
1/4.70
0/4.3
(a)/(c).sup.(7)
1/0.01
1/2.0
1/0.23
1/0.23
1/1.6
1/0.07
-- 1/0.23
__________________________________________________________________________
Comparative Example No.
9 10 11 12 13 14 15
__________________________________________________________________________
Polyvinyl Acetate.sup.(1)
Saponification Degree
30 90 90 90 90 90 90
Polymerization Degree
500 50 1000 500 500 500 500
weight % 3.5 3.5 3.5 3.5 1.0 10.0
3.5
Water-Soluble Nylon.sup.(2)
1.7 1.7 1.7 0.5 1.7 1.7 1.7
(weight %)
Water-Soluble Amino Resin
Type.sup.(3) M M M M M M M
weight % 0.8 0.8 0.8 0.8 0.8 0.8 0.1
Anti-Mold Agent.sup.(4)
0.3 0.3 0.3 0.3 0.3 0.3 0.3
(weight %)
Anti-Bacterial Agent.sup.(5)
0.1 0.1 0.1 0.1 0.1 0.1 0.1
(weight %)
Weight Ratio
(b)/((a) + (c)).sup.(6)
1/2.53
1/2.53
1/2.53
1/8.6
1/1.06
1/6.35
1/2.12
(a)/(c).sup.(7)
1/0.23
1/0.23
1/0.23
1/0.23
1/0.8
1/0.08
1/0.03
__________________________________________________________________________
Note
.sup.(1) At least partially saponified polyvinyl acetate selected from:
(a) SMR30HH manufactured by ShinEtsu Chemical Co., Ltd., having a
saponification degree of 90 and a polymerization degree of 500; and
(b) SMR20L manufactured by ShinEtsu Chemical Co., Ltd. having a
saponification degree of 30 and a polymerization degree of 500.
.sup.(2)-(8) Same as .sup.(2)-(8), respectively, in Table 1.
TABLE 4
______________________________________
Com- Hydrophilic
para. Nature Water
Ex- After Dissolu- Mildew
ample At Wetting
tion Re-
Ad- Proofing
No. Odor Start Cycle sistance
hesion
Property
______________________________________
1 Excel. Excel. Poor Poor Good Poor
2 Excel. Poor Poor Excel. Excel.
Excel.
3 Excel. Poor Poor Excel. Excel.
Fair
4 Poor Excel. Poor Poor Poor Poor
5 Fair Excel. Poor Poor Fair Poor
6 Excel. Excel. Poor Poor Poor Poor
7 Poor Excel. Fair Fair Good Fair
8 Excel. Fair Poor Excel. Excel.
Excel.
9 Excel. Fair Poor Excel. Excel.
Good
10 Good Excel. Fair Poor Fair Poor
11 Excel. Good Fair Excel. Excel.
Excel.
12 Excel. Poor Poor Excel. Excel.
Good
13 Good Excel. Good Poor Fair Fair
14 Good Fair Fair Poor Fair Good
15 Good Excel. Poor Poor Fair Poor
______________________________________
As described above in detail, since the surface treatment chemicals
according to the present invention comprises at least partially saponified
polyvinyl acetate, water-soluble nylon and a water-soluble amino resin in
a particular weight ratio, it can provide coatings having excellent
hydrophilic nature, water dissolution resistance, adhesion to aluminum
members with substantially no odor.
Thus, the surface treatment chemicals according to the present invention
are highly suitable for the surface treatment of aluminum members such as
fins of heat exchangers, etc.
The present invention has been described by Examples, but it should be
noted that any modifications are possible unless they deviate from the
scope of the present invention defined by the claims attached hereto.
Top